This is the new updated edition of the first book in the bestselling Uncovering Student Ideas in Science series. Like the first edition of volume 1, this book helps pinpoint what your students know (or think they know) so you can monitor their learning and adjust your teaching accordingly. Loaded with classroom-friendly features you can use immediately, the book includes 25 “probes”—brief, easily administered formative assessments designed to understand your students’ thinking about 60 core science concepts.

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The purpose of this assessment probe is to elicit students’ ideas about an Earth material, rocks. The probe is designed to determine whether students can distinguish between humanmade, “rocklike” materials and geologically formed rock materials of various origins, even though it may have been shaped by humans. The probe reveals whether students have a geologic conception of a rock.

Justified list

Rock, minerals, natural resources, Earth materials

The items on the list that are rocks are coal, hardened lava, limestone, a gravestone, iron ore, marble statue, and granite. Simply, a rock can be defined as any solid mass of mineral or mineral-like matter that occurs naturally as part of our planet and is formed over long periods of time (Lutgens and Tarbuck 2003). Some rocks, such as limestone, are composed almost entirely of one mineral—in this case, impure masses of calcite. Other rocks occur as aggregates of two or more minerals. For example, granite is a common rock composed of the minerals quartz, hornblende, and feldspar. A few rocks are composed of nonmineral matter. Chalk is a rock made from the shells of foraminifera. Coal is a rock formed over millions of years by the hardening of layers of decomposed plant material subjected to pressure.

Some of the items on the list are rocklike in that they are similar to rock material but are not naturally formed through long-term geologic processes. The cement block, piece of clay pot, brick, asphalt, glass, and concrete are all made by combining some rock material with other materials and reshaping them through a human-made process, not a geologic one. The material itself is not “rock.” However, the gravestone and marble statue are rock, even though they have been reshaped and polished through a human-made process, because the material they are made of was formed through a geologic process and the original composition is unchanged. The material is still rock; only the shape and texture have changed.

Coral is made by living processes, not geologic processes, and can form over relatively short time scales. Soft-bodied organisms secrete calcium carbonate to make hard, rocklike casings that protect their soft bodies. These “community casings” result in the formation of coral reefs.

Mud is a mixture of silt, clay, and water. Silt and clay are fine rock fragments. Mud can dry out, forming hard cakes that appear rocklike. However, it takes long periods of geologic time for dried mud to harden (lithify) into solid sedimentary rock such as shale.

Elementary Students

Elementary students observe and classify objects and materials based on their properties. Students should have opportunities to become familiar with the variety of objects and materials in their local environment, including rocks and objects made from rocks. At this level, students begin to understand that rocks can come in natural forms and that rocks are considered natural resources that can be cut, shaped, and polished by humans for various uses. They begin to understand how some objects and materials exist naturally and others are made by humans combining materials from the environment in new ways, based on the properties of the materials.

Middle School Students

Students investigate how Earth materials such as rocks are formed. They develop an understanding of how rocks are formed through long-term geologic processes, resulting in a variety of sedimentary, igneous, and metamorphic rocks. Students can begin to trace the composition of rocks and minerals back to the geologic processes that formed them. They can contrast this formation with shortterm human processes developed through engineering design that result in rocklike materials such as cement. In their study of natural resources, they recognize that rock is a natural resource that can be reshaped by humans without changing its composition or can be crushed and combined with other materials to form a new, hard material.

High School Students

Students at this level refine their understanding of the geologic processes that form rocks and the chemical composition and origin of minerals that make up rocks. They have a greater awareness of the long-term, geologic processes that form rocks. They learn about chemical processes engineered by humans, which result in rocklike mixtures such as asphalt, concrete, and cement. In biology, they recognize living processes that form hard, rocklike casings such as coral and mollusk shells and link this to the idea of biogeochemical cycles. At this level, combined with their knowledge of chemistry, students have greater familiarity with synthetically produced materials and are more apt to differentiate them from materials produced through geologic processes.

This probe can be used with students in grades 3–8. Make sure students are familiar with the materials and objects on the list. You may choose to show examples (actual or photographic) of the materials or objects or point out ones they are familiar with in their local environment, such as a cement sidewalk or asphalt road. Words can also be written on cards or combined with pictures and used as a card sort activity, sorting cards into “rock,” “not rock,” and “unsure.” For middle school students who are familiar with examples of igneous rocks, consider replacing the term hardened lava with basalt or pumice.

• Some students regard rock as being made of only one substance and thus have difficulty recognizing granite as rock (Driver et al. 1994).
• Freyberg (1985) found that the word rock is used in many different ways in our common language, contributing to the confusion over what a rock is geologically.
• Some students use “heaviness” to describe rocks. When students were shown different types of rocks and asked whether they were rocks, several students thought pumice was too light to be a rock (Osborne and Freyberg 1985).
• In studies by Happs (1982, 1985), students had difficulty making the distinction between “natural” things and those created or altered by humans. For example, some students considered brick a rock because part of it comes from natural material. Conversely, some students thought cut, smooth, polished marble was not a rock because humans made it smooth and so it was no longer natural.

Keeley, P. 2013. Is it a rock? Continuous formative assessment. Science and Children 50 (8): 34–37.

Keeley, P. 2014. Is it a rock? Continuous formative assessment. In What are they thinking? Promoting elementary learning through formative assessment, P. Keeley, 173–180. Arlington, VA: NSTA Press.

Plummer, D., and W. Kulman. 2005. Rocks in our pockets. Science Scope 29 (2): 60–61.

Rivet, A. E. 2017. Core idea ESS2: Earth’s systems. In Disciplinary core ideas: Reshaping teaching and learning, ed. R. G. Duncan, J. Krajcik, and A. E. Rivet, 205–223. Arlington, VA: NSTA Press.

Varelas, M., and J. Benhart. 2004. Welcome to rock day. Science and Children 40 (1): 40–45.

• A related version of this probe, “Is a Brick a Rock?,” is available for K–2 students in Uncovering Student Ideas in Primary Science, Volume 1 (Keeley 2013).
• When teaching about rocks, take time to elicit students’ conceptions of what a rock is. Although students may have had several opportunities to learn about rocks during their K–8 experiences, do not assume that they have a geologic conception of what a rock is. Students may be able to define rock, name types of rocks, and describe the geologic processes that formed them, but they may still identify human-made materials such as brick as rocks.
• Emphasize the long periods of geologic time it takes to form rock and compare the long-term stages of the rock cycle with the short period of time it takes to make a brick or a cement block.
• When elementary students describe physical properties of objects, include rocks in the study of properties. Rocks can be used to demonstrate how a physical property may change, but the material is still the same. For example, show students a rough piece of granite and a smooth, polished piece of granite, noting that they are still the same material, although humans have changed the property of texture.
• Compare and contrast naturally formed objects with objects made or reformed by humans. In the latter category, have students place objects into two groups: (1) those objects made entirely from natural materials that have not been changed in composition when reshaped by humans (e.g., the marble statue) and (2) those that contain some natural material, combined with other materials to make new material with a different composition that does not exist in a natural state (e.g., concrete or brick).
• Have students investigate the materials that make up brick, concrete, cement, and asphalt. Connect this to engineering and technology, noting how humans use natural resources and scientific knowledge about materials to design and make new types of materials for construction. • For older students, add more challenging items to the list, such as glacier ice, petrified wood, diamond, magma, fossilized bone, pearl, chalk, ceramic tile, salt, and copper.